1. Field of the Invention
The present invention relates to a seat belt system for restraining an occupant in a seat and, more specifically, to an improved four point seat belt apparatus.
2. Relevant Technology
Seat belt apparatuses are known to increase the safety of occupants in various motorized vehicles. Seat belt use is often cited as being the most useful line of defense in reducing accident injury. The recognition of seat belts has been reflected in safety programs advocating their use and state legislation mandating their use. Seat belts vary in their configuration but one of the most common seat belts is the lap belt apparatus. The lap belt includes right and left belts which traverse an occupant""s lap and are secured to each other proximate to the occupant""s mid abdomen. Securement of the lap belts is achieved through the use of a buckle which enables fastening to secure an occupant. Such lap belts may be found in almost all seats in automobiles and planes throughout the world.
Although conventional lap belt apparatuses are well used and accepted they do not limit movement of an occupant""s head and torso. Thus, although the lower body is restrained, the upper body will experience rapid and dangerous movement during an accident. This is particularly dangerous for passengers in the front seat of an automobile who may strike the dashboard or windshield during an accident.
An improvement therefore is to introduce shoulder straps and harnesses to limit upper body movement. Single shoulder straps which traverse diagonally across an occupant""s body are used in automobiles and aircraft throughout the world. To a lesser extent, double shoulder straps which traverse vertically across an occupant""s upper body are also widely used in vehicles. Double shoulder straps provide additional contact with the upper torso to further limit upper body movement and provide additional safety. Seat belt apparatuses which incorporate double shoulder straps and lap belts are commonly referred to as four point seat belt systems.
A common concern with the four point seat belt system is that the buckle must preferably remain centered over the mid sagittal plane, i.e. on the middle of the occupant""s abdomen. If the buckle does not remain in such a position, there will be an uneven load distribution on the different components of the seat belt apparatus. This may allow the occupant to twist in the seat and increases the risk of the occupant sliding between the shoulder belts. Loose contact with the shoulder belts may result in injury in the event of an accident.
Another concern is to prevent the buckle from sliding up on the occupant""s abdomen during a collision and causing the lap belt loops to disengage from their contact with the iliac crests of the pelvic bone. This creates reduced retention of the pelvis, which can result in excessive loads on the abdomen and reduced seat belt restraint performance. Such conditions may lead to serious injury during the collision.
Thus, it would be an advancement in the art to provide a four point seat belt apparatus which retains the position of the buckle over the abdomen.
It would be a further advancement in the art to provide a four point seat belt apparatus which prevents upward movement of the buckle during a collision.
Such an apparatus is disclosed and claimed herein.
The present invention solves the foregoing problems by providing a four point seat belt apparatus with superior safety capability. The seat belt apparatus is used in combination with a seat and includes a seat belt webbing which traverses an occupant""s body. The webbing includes first and second lap belts and first and second shoulder belts. The lap belts are secured at their one ends to a lap belt retractor which allows for extraction and retraction of the lap belts during normal use and locking of the lap belts during accident conditions.
In one embodiment, the lap belt retractor is secured to a forward and low position relative to the seat. The opposing ends of the lap belts are secured in a fixed manner to a lap belt anchor. The lap belt anchor is secured to a rearward and low position in the seat. The lap belt anchor may further incorporate a pretensioner to create a downward and rearward pull on the lap belts. The lap belts slidably engage a buckle assembly along a mid section of the lap belts. The lap belt retractor is configured to simultaneously retract the first and second lap belts to thereby retain the position of the buckle assembly over the mid abdomen section of an occupant.
The first and second shoulder belts are secured at one end to first and second shoulder belt retractors. The shoulder belt retractors are secured to the upper portion of the seat or to a fixed surface proximate to a location behind the occupant""s head. The shoulder belt retractors allow for extraction and retraction of the shoulder belts under normal conditions, and fixed positioning of the shoulder belts during an accident. The opposing ends of the shoulder belts are secured in a fixed manner to the buckle assembly. The lap belt retractor and the lap belt anchor together pull the buckle assembly forward and downward to a lower position. The pretensioner creates a downward force pulling the buckle assembly rearward to better contact the iliac crests of the occupant""s pelvis.
These features and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.